1. Field of the Invention
The present invention relates to an image forming apparatus and, in particular, to a construction for discharging sheets with images formed thereon.
2. Related Background Art
In a conventional image forming apparatus, such as a copying machine or a printer, a sheet on which an image has been formed is discharged onto a sheet discharging portion. When discharging a sheet with an image formed thereon with the front and rear surfaces of the sheet reversed, the sheet is reversed by a sheet reversing path before being discharged. This sheet reversing path is also used when performing two-sided printing.
FIG. 15 shows an example of a conventional image forming apparatus having such a sheet reversing path. In this image forming apparatus, a sheet with an image formed thereon is discharged in the direction of the arrow K by discharging rollers 161. When discharging a sheet after reversing it, a flapper 162 is switched and the sheet with an image formed on the front surface (first surface) thereof is conveyed to a reversing path 167. Then, reversing rollers 165 are rotated in the reverse direction, and the flapper 162 is restored to the original position.
When forming images on both sides of a sheet, the sheet S1 with an image formed on the front surface (first surface) thereof is conveyed to the reversing path 167 by way of a conveying roller pair 166 by switching the flapper 162. Thereafter, when the trailing edge of the sheet passes a flapper 164 provided in the reversing path 167, the reversing rollers 165 are rotated in the reverse direction, and the flapper 164 is switched, whereby the sheet is fed to an intermediate tray 168. In this image forming apparatus constructed as described above, the sheet reversing path 167 is arranged perpendicular to the sheet discharging direction.
FIG. 16 shows another example of a conventional image forming apparatus having a sheet reversing path. In this image forming apparatus, the sheet on which image formation has been effected is discharged not to the side of the apparatus main body but to the interior of the apparatus main body.
In this type of image forming apparatus, a sheet contained in a sheet feeding cassette 21 or an option sheet feeding cassette 103 provided as an option is conveyed to an image forming portion 1 by a sheet feeding portion 2 and a toner image is transferred thereto by an electrophotographic process means 150. Thereafter, the toner image is fixed by a fixing apparatus 151, and the sheet is conveyed to a sheet discharging portion 4.
FIG. 17 shows the construction of the sheet discharging portion 4. As shown in the drawing, this image forming apparatus is equipped with two sheet discharging trays 41 and 42. The sheet to which the toner image has been fixed is discharged onto the first sheet discharging tray 41 by a first discharging roller 51, or onto the second sheet discharging tray 42 situated above the first sheet discharging tray 41 by a second discharging roller 52.
This image forming apparatus is capable of two-sided printing. When performing two-sided printing, a part of the sheet which has passed the fixing apparatus 151 is temporarily discharged onto the first sheet discharging tray 41 by a longitudinal path roller 57 and the first discharging roller 51. Thereafter, when the trailing edge of the sheet has passed a first flapper 58, the longitudinal path roller 57 and the first discharging roller 51 are rotated in the reverse direction to convey the sheet to a two-sided path 152. In this case, the sheet reversing path is the same as the sheet conveying path. Further, the sheet reversing path is perpendicular to the direction of the arrow A in which the sheet is discharged.
Note that the image forming apparatus shown in this drawing functions as both a copying machine and a facsimile apparatus; it is a so-called digital multifunction printer which forms an image by converting the read image information (optical signal) of the original into an electric signal.
In the case of such a multifunction printer, the sheets discharged onto the first and second sheet discharging trays 41 and 42 are rather poor in visibility. Further, it is sometimes required that a sheet conveyed by, for example, a facsimile apparatus should be separately stored. Thus, as shown in FIG. 18, for example, a third sheet discharging tray 43 is detachably provided on the outer side surface of the apparatus main body, and the sheet is discharged onto this third sheet discharging tray 43 by a third sheet discharging roller 53.
When the third sheet discharging tray 43 is thus provided, the sheet to which the toner image has been fixed is discharged onto a third sheet discharging tray 43 by the longitudinal path rollers 54 and 57 and the third discharging roller 53, with the transfer side being directed upwards.
However, when thus discharging the sheet onto the third sheet discharging tray 43, the sheet is discharged with the transfer side being directed upwards, so that when the sheet which has been conveyed up to the longitudinal path roller 54 is conveyed as it is toward the third discharging roller, the page order is reversed.
To avoid reversal in page order, it is necessary to provide a reversing path anew, which leads to an increase in apparatus size. Further, since reversing rollers, etc. have to be provided in the reversing path, an increase in cost and a rather complicated structure are involved.
The present invention has been made with a view toward solving the above problem. It is an object of the present invention to provide an image forming apparatus capable of discharging sheets without involving any change in page order without having to provide a sheet reversing path anew.
The present invention relates to an image forming apparatus in which an image is formed on sheet by an image forming portion and the sheet is discharged, comprising a main body portion, first discharging means capable of normal and reverse rotation and adapted to discharge the sheet with the image formed thereon to a first discharging portion provided on one side of the main body portion, second discharging means adapted to discharge the sheet with the image formed thereon to a second discharging portion provided on the other side of the main body portion, a first sheet conveyance route for conveying the sheet with the image formed thereon toward the first discharging means, and a second sheet conveyance route for conveying the sheet with the image formed thereon toward the second discharging means, the apparatus being characterized in that sheet discharging direction control means is provided, which, when discharging the sheet to the second discharging portion, causes the sheet with the image formed thereon to be conveyed toward the first sheet conveyance route, and then reverses the first discharging means to convey the sheet toward the second sheet conveyance route.
Also, according to the present invention, an image forming apparatus is characterized in that the sheet discharging direction control means has conveyance route switching means which can be displaced to a first position for conveying the sheet with the image formed thereon toward the first sheet conveyance route and a second position for conveying the sheet conveyed by the first discharging means adapted to be reversed after conveying the sheet toward the first sheet conveyance route, toward the second sheet conveyance route.
Also, according to the present invention, an image forming apparatus is characterized in that the conveyance route switching means is held at the second position by a biasing member and adapted to be displaced to the first position by being pressed by the sheet.
Also, according to the present invention, an image forming apparatus is characterized in that the first discharging portion is a predetermined discharging portion of a plurality of discharging portions provided on one side of the main body portion.
Also, according to the present invention, an image forming apparatus is characterized in that the apparatus main body is provided with a sheet discharging space which is open sidewise, the plurality of discharging portions being provided in the sheet discharging space.
Also, according to the present invention, an image forming apparatus is characterized in that the second discharging portion is detachably provided on an outer side surface of the apparatus main body at a position opposite to the sheet discharging space.
Also, according to the present invention, an image forming apparatus is characterized in that the second discharging portion is a post-processing device for performing post-processing on sheets.
Further, according to the present invention, the sheet discharging direction control means comprises a main body portion, first discharging means capable of normal and reverse rotation and adapted to discharge a sheet with an image formed thereon onto a first discharging portion provided on one side of the main body portion, second discharging means adapted to discharge a sheet with an image formed thereon onto a second discharging portion provided on the other side of the main body portion, a first sheet conveyance route for conveying a sheet with an image formed thereon toward the first discharging means, and a second sheet conveyance route for conveying a sheet with an image formed thereon toward the second discharging means. Then, when discharging a sheet onto the second discharging portion, the sheet with an image formed thereon is conveyed toward the first sheet conveyance route, and then the first discharging means is reversed before conveying the sheet toward the second sheet conveyance route.